1. Field of the Invention
The present invention relates to a method for driving a liquid crystal light modulating device, and a liquid crystal light modulating device, in particular, a method for driving a liquid crystal light modulating device wherein a liquid crystal composition comprising a chiral dopant and a dichroic dye is used, and a liquid crystal light modulating device.
2. Description of the Related Art
As a method for switching a light-scattered (light-shielded) state and a transparent state in liquid crystal light modulating devices, methods as described below are disclosed.
For example, “Development of Chromic Material”, edited by Kunihiro Ichimura (published by CMC Publishing Co., Ltd. in 2000), pp. 226-236 discloses, as a method for switching between a state of light-scattered white and a state of transparent through applied voltage. In the method, capsules in which liquid crystals are encapsulated are dispersed into a polymer. When the circuit is opened, alignment of liquid crystals is random. Accordingly, light is reflected irregularly by difference in refractive index between liquid crystals and the polymer, thereby scattering (light shielding occurs). On the other hand, when the circuit is closed, alignment of liquid crystals is uniform. Accordingly, it is transparent by conformance in refractive index between the long axis direction of liquid crystals and the polymer. Therefore, in the method, switching can be made between a white scattered state and a transparent state by applied voltage.
However, according to this method, in order to make a liquid crystal light modulating device into a colored state, it is necessary to dissolve a dichroic dye into the liquid crystal. But the coating film of the capsules is dyed with the dichroic dye, or the dichroic dye is easily aligned along the polymer coating film so that responsiveness to the voltage is lost. Thus, the method has a problem in that when the liquid crystal is transparent, the transmittance thereof becomes low.
WO 2002/093241 discloses a method of: mixing an uncured ultraviolet-curable resin, a polymerization initiator, a liquid crystal and a dichroic dye; and radiating ultraviolet rays to the mixture to cure the resin, whereby the polymer and the liquid crystal undergo phase-separation to form an interface between the polymer and the liquid crystal, and thus a device wherein the present system is used is operated by the same principle as used in the above-mentioned liquid crystal light modulating device.
However, this method has a problem in that the dye is decomposed by the UV-radiation or with the polymerization initiator so that the colorability of the dye declines.
As described above, the driving methods of the prior art each have problems to be overcome.